This invention relates to a reactor for catalytically converting gases which contain carbon oxides, hydrogen and water vapor into methane at temperatures between about 250.degree. C and 550.degree. C and under pressures in the range of 10-80 kg/cm.sup.2, comprising a substantially cylindrical outer shell, which is provided at opposite end faces with a gas inlet and a gas outlet.
A catalytic methanation stage is often included in a process of producing high-methane gases, such as synthetic natural gas. In a preceding process step, a rich gas is produced, which consists mainly of methane and contains also carbon monoxide, carbon dioxide, and hydrogen. The gas mixture to be methanated contains in most cases also water vapor in the amount required for methanation.
The reactor according to the invention is intended for such methanation, which is carried out in most cases with the aid of nickel-containing catalysts, which contain 30-60% by weight nickel on a support. Supports of various kinds, such as alumina, magnesium silicate or magnesium spinel, may be used for this purpose. The catalytic reaction of carbon oxides and hydrogen is an exothermic reaction. For this reason, known methanation reactors comprise a plurality of superimposed catalyst beds, which are cooled with water. Shaft reactors are also known, in which the gas mixture to be reacted flows through a single, uninterrupted catalyst bed.
In connection with a methanation reactor which is large in volume and in excess of 3 m in diameter, special problems arise because such reactors can be transported only with very great difficulty or must be erected directly on the site of the gas-producing plant. Another difficulty resides in the differential thermal expansion of the top and bottom portions of the reactor as a result of the exothermic nature of the reaction. This differential thermal expansion gives rise to different shear stresses in the reactor, particularly in its outer shell.